Traditionally, the way painting was done in GTK+ was with the
"expose-event" handler, where you'd use GDK methods to do drawing on
your surface. In GTK+ 2.24, we added cairo support with gdk_cairo_create,
so you could paint your graphics with cairo.
Since then, we've added client-side windows, double buffering, the paint
clock, and various other enhancements, and the modern way to do drawing
is to connect to the "draw" signal on GtkWidget, which hands you a
cairo_t. To do double-buffering, the cairo_t we hand you is actually on
a secret surface, not the actual backing store of the window, and when
the draw handler completes we blit it into the main backing store
atomically.
The code to do this is with the APIs gdk_window_begin_paint_region,
which creates the temporary surface, and gdk_window_end_paint which
blits it back into the backing store. GTK+'s implementation of the
"draw" signal uses these APIs.
We've always sort-of supported people calling gdk_cairo_create
"outside" of a begin_paint / end_paint like old times, but then you're
not getting the benefit of double-buffering, and it's harder for GDK to
optimize.
Additionally, newer backends like Mir and Wayland can't actually support
this model, since they're based on double-buffering and swapping buffers
at various points in time. If we hand you a random cairo_t, we have no
idea when is a good time to swap.
Remove support for this.
This is technically a GDK API break: a warning is added in cases where
gdk_cairo_create is called outside of a paint cycle, and the returned
surface is a dummy that won't ever be composited back onto the main
surface. Testing with complex applications like Ardour didn't produce
any warnings.
It seems that some backends implemented get_root_origin wrong
and returned the client window coordinates, not the frame window
coordinates. Since it's possible to implement generically for all
windows, let's do that instead of having a separate impl vfunc.
Instead of destroying the surface in the backend if this is
unable to resize, let the core code do it, and do it properly.
Based on a patch by Benjamin Otte.
https://bugzilla.gnome.org/show_bug.cgi?id=725172
We've long had double precision mouse coordinates on wayland (e.g.
when rotating a window) but with the new scaling we even have it on
X (and, its also in Xinput2), so convert all the internal mouse/device
position getters to use doubles and add new accessors for the
public APIs that take doubles instead of ints.
When the toplevel is a GdkOffscreenWindow which doesn't
implement the set_device_cursor() vfunc, we would have
crashed. Implement a dummy ->set_device_cursor vfunc.
https://bugzilla.gnome.org/show_bug.cgi?id=675809
This fixes issues where the new default bg of transparent
didn't work, making offscreen windows black.
I don't think this is a practical performance problem.
Offscreen windows are rarely used and generally used for
graphics tricks like alpha anyway.
Just a noop that is better than crashing in the case this is called
(it can be called for a toplevel GtkWindow that is parented into
another widget by setting gtk_widget_set_parent_window to an offscreen
window).
... instead of _gdk_drawable_ref_cairo_surface() where appropriate.
Also, don't implement the drawable->create_cairo_surface vfunc anymore.
This is in preparation for the split of GdkWindow from GdkDrawable.
Add signal GdkWindow::create-surface which allows to use any
surface type as storage for offscreen windows.
Test the new signal in tests/gdkoffscreenbox.c
I don't think it's necessary to clear the backing surface when showing
the window, as we're going to repaint it anyway. If it's needed, we can
implement it again using internal APIs, as the public window_clear()
APIs are going away.
